BRITISH MARINE TURBELLARIA. 187 



The terminations of generic names have not hitherto been formed 

 in an uniform way. Von Graff changed the terminations of all the 

 older generic names, such as Acmostomum, to Acmostoma, whereas 

 Lang retains the -urn form. In the present paper I have followed 

 these authors. It would, however, seem advisable in the future to 

 adopt either one termination or the other, right through the group. 

 Spengel's* Latinised form of ''Alloioccela" (Alloeocoela) is adopted. 



II. — Systematic. 



TURBELLARIA. 

 Sub-order l.-RHABDOC(ELIDA. 



A. AG (EL A. 



A digestive cavity absent. Mouth ventral, hading indirectly through the 

 ■pharynx into the parenchyma. A "frontal gland " and otolith 

 present. Nervous system consisting of a brain and peripheral nervous 

 sheath. Hermaphrodite. Testes follicular, rarely compact. 



Family PROPOPJDiE. 



Acala icith a common genital pore. 



Genus 1. — Proporus, v. Graff 

 ( = Schizoprora, Schmidt, 28). 



Proporidce without spermotheca ,f 



1. Proporus venenosus (0. Schmidt, 28). 



Length 1 mm. Body elongate, cylindrical, rounded at both ends. 

 Colour bright yellow, due to diffused granular pigment. Epidermis 

 ciliated, containing numerous rhabdites, some free, some grouped in 

 formative cells. These pyriform groups are specially abundant 

 towards the hinder end, giving a spinous appearance to the surface. 

 The mouth lies just beneath the anterior end ; circular at rest, it 

 becomes slit-like during movement. The pharynx is a direct 

 invagination of the anterior end (v. Graff, 'Acoela,' pi. x, fig. 5). It is 



" 'Gotting. gelehrte Anzeigen,' March 1st, 1884, p. 183, note. 



t The definitions of families, sub-families, and genera are taken from 

 v. Graff (53). 



